This is the compatibility list for oyur motherboard: http://www.intel.com/support/motherboards/desktop/D865GLC/sb/CS-026965.htm
So official no you cannot...it may work though you would have tyo try but i wouldnt hold my breath!
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The answer is NO.
This is because your motherboard is a Socket 478 motherboard while all Socket 478 Intel processors ever manufactured have all been single-core. There has never been a dual-core Intel processor ever manufactured for that socket type. All dual-core processors ever manufactured will not even physically fit your D865GLC's socket since the processors are not pin-compatible at all.
In other words, if you want a multi-core processor, you will have to replace not only the processor, but the desktop board and the memory as well.
Hope this helps.